Thyroid Nodules

The thyroid gland is located in the lower front of the neck, below the voicebox (larynx) located in the upper part of the neck, and above the collarbones.

A thyroid nodule is a lump in or on the thyroid gland. Thyroid nodules are common and detected in about six percent of women and one to two percent of men; they are less common in younger patients and occur 10 times as often in older individuals, but are usually not diagnosed. Sometimes several nodules will develop in the same person. Any time a lump is discovered in thyroid tissue, the possibility of malignancy (cancer) must be considered. More than 95 percent of thyroid nodules are benign (non-cancerous), but tests are needed to determine if a nodule is cancerous.

Benign nodules include:

Multinodular goiter, also called a non-toxic goiter. The word goiter means the thyroid gland has grown too large. This usually happens when the pituitary gland (in the brain) creates too much thyroid stimulating hormone (TSH). If the goiter is small, the problem may be treated with thyroid hormone pills. Surgery is needed if the goiter is large or does not stop growing after taking thyroid hormones. A large thyroid gland can press against the trachea (windpipe) or esophagus (food tube) and cause difficult breathing or eating.

Chronic thyroiditis (Hashimoto's disease) is an inflammation of the thyroid gland that develops slowly. It frequently leads to a decreased function of the thyroid (hypothyroidism). Middle-aged women are most commonly affected. Thyroiditis occurs when the body's own immune system destroys the cells in the thyroid gland. Chronic thyroiditis is most common in women and people with a family history of thyroid disease.

Benign follicular adenomas. The word follicular means the cells look like a group of small circles under a microscope. If the follicular cells are contained within the nodule, the condition is called benign. If the cells have invaded the surrounding tissue, the diagnosis is cancer. The nodule must be surgically removed and examined under a microscope to look for evidence of invasion into the normal thyroid tissue or blood vessels.

Thyroid cysts are nodules filled with fluid. They can be small or large and might appear suddenly. If a nodule has both fluid and solid parts, it is called a complex nodule. They need to be surgically removed if they cause neck pain or difficultly swallowing.

Symptoms

Many patients with thyroid nodules have no symptoms whatsoever, and are found by chance to have a lump in the thyroid gland on a routine physical exam or an imaging study of the neck done for unrelated reasons (CT or MRI scan of spine or chest, carotid ultrasound, etc). However, a minority of patients may become aware of a gradually enlarging lump in the front portion of the neck, and/or may experience a vague pressure sensation or discomfort when swallowing. Obviously, finding a lump in the neck should be brought to the attention of your physician, even in the absence of symptoms.

Causes

Nodules can be caused by a simple overgrowth of "normal" thyroid tissue, fluid-filled cysts, inflammation (thyroiditis), or a tumor (either benign or cancerous). Most nodules were surgically removed until the 1980s. In retrospect, this approach led to many unnecessary operations, since fewer than 10 percent of the removed nodules proved to be cancerous. Most removed nodules could have simply been observed or treated medically.

Diagnosis

Fine Needle Biopsy

A thyroid fine needle biopsy is a simple procedure that can be performed in the physician's office. Some physicians numb the skin over the nodule prior to the biopsy, but it is not necessary to be put to sleep, and patients can usually return to work or home afterward with no ill effects. This test provides specific information about a particular patient's nodule, information that no other test can offer short of surgery. Although the test is not perfect, a thyroid needle biopsy will provide sufficient information on which to base a treatment decision more than 85 percent of the time it an ultrasound is used eliminating the need for additional diagnostic studies.

Use of fine needle biopsy has drastically reduced the number of patients who have undergone unnecessary operations for benign nodules. However, about 10 - 20 percent of biopsy specimens are interpreted as inconclusive or inadequate, that is, the pathologist cannot be certain whether the nodule is cancerous or benign. This situation is particularly common with cystic (fluid-filled) nodules, which contain very few thyroid cells to examine, and with those nodules composed of a particular cell type called follicular. In such cases, a physician who is experienced with thyroid disease can use other criteria to make a decision about whether or not to operate. The fine needle biopsy can be repeated in those patients whose initial attempt failed to yield enough material to make a diagnosis. Many physicians use thyroid ultrasonography to guide the needle's placement.

Thyroid Scan

A thyroid scan is a picture of the thyroid gland taken after a small dose of a radioactive isotope normally concentrated by thyroid cells has been injected or swallowed. The scan tells whether the nodule is hyperfunctioning (a "hot" nodule), or taking up more radioactivity than normal thyroid tissue does, taking up the same amount as normal tissue (a "warm" nodule), or taking up less (a "cold" nodule). Because cancer is rarely found in hot nodules, a scan showing a hot nodule eliminates the need for fine needle biopsy. If a hot nodule causes hyperthyroidism, it can be treated with radioiodine or surgery.

Neither a thyroid scan nor radioiodine treatment should ever be given to a pregnant woman! Small amounts of radioactive iodine will also be excreted in breast milk. Since radioiodine could permanently damage the infant's thyroid, breast-feeding is not allowed. If radioiodine is inadvertently administered to a woman who is subsequently discovered to be pregnant, the advisability of terminating the pregnancy should be discussed with the patient's obstetrician and endocrinologist. Therefore, prior to administering diagnostic or therapeutic radioiodine treatment, pregnancy testing is mandatory whenever pregnancy is possible.

Fortunately, the vast majority (90 - 95 percent) of thyroid nodules are benign. Unfortunately, thyroid scans show that most thyroid nodules, both benign and malignant, are cold or nonfunctioning. Therefore, although almost all thyroid cancers are nonfunctional on scan, the majority of nonfunctional nodules are benign. For this reason, thyroid scans are of relatively little value in most patients unless TSH levels are toward the lower end of the normal range or below the normal range. For more information on TSH levels please visit the AACE Thyroid Awareness web page.

Ultrasound

Thyroid ultrasoundography is a procedure for obtaining pictures of the thyroid gland by using high-frequency sound waves that pass through the skin and are reflected back to the machine to create detailed images of the thyroid. It can visualize nodules as small as 2 to 3 mm. Ultrasound distinguishes thyroid cysts (fluid-filled nodules) from solid nodules. Many nodules have both solid and cystic components, and very few purely cystic nodules occur. Recent advances in ultrasonography helps physicians identify nodules which are more likely to be cancerous.

Thyroid ultrasonography is also utilized for guidance of a fine needle for aspirating thyroid nodules. Ultrasound guidance enables physicians to biopsy the nodule to obtain an adequate amount of material for interpretation. Such guidance allows the biopsy sample to be obtained from the solid portion of those nodules that are both solid and cystic, and it avoids getting a specimen from the surrounding normal thyroid tissue if the nodule is small.

Even when a thyroid biopsy sample is reported as benign, the size of the nodule should be monitored. A thyroid ultrasound examination provides an objective and precise method for detection of a change in the size of the nodule. A nodule with a benign biopsy that is stable or decreasing in size is unlikely to be malignant or require surgical treatment.

Treatments

Your Cedars-Sinai endocrinologist will use the above-mentioned tests to arrive at a recommendation for optimal management of your nodule. Most patients who appear to have benign nodules require no specific treatment, and can simply be followed. Some physicians prescribe levothyroxine with hopes of preventing nodule growth or reducing the size of cold nodules, while radioiodine may be used to treat hot nodules.

If cancer is suspected, surgical treatment will be recommended. The primary goal of therapy is to remove all thyroid nodules that are cancerous; and, if malignancy is confirmed, remove the rest of the thyroid gland along with any abnormal lymph nodes. If surgery is not recommended, it is important to have regular follow-up of the nodule by a physician experienced in such an evaluation.